This vaccine is based on the idea that we live in an environment that is too clean

Dr Ratko Djukanovic, University of Southampton

Dr Ratko Djukanovic, of the University of Southampton, who is leading the research said: "This is a natural protector."

Previous studies have found the bacteria to be useful in the treatment of TB and cancer.'

The university is now recruiting 120 patients with asthma, whose symptoms persist despite using inhaled steroids, to test the vaccine.

'Hygiene hypothesis'

Some will be vaccinated with the bacteria, which although from the same family as the tuberculosis bacterium, does not cause any disease.

Dr Djukanovic, senior lecturer in medicine and
honorary consultant physician at the university, said: "People can be exposed to this bacteria daily without
harm - it is commonly found in household taps."

There is a theory, called the "hygiene hypothesis", backed by Dr Djukanovic, which suggests measures such as the overzealous cleaning of houses has meant immune systems lack practice fighting bacteria and viruses.

That means when they come into contact with an allergen, the immune systems do not destroy it as they should.

They produce messenger proteins, called cytokines, which then stimulate white
blood cells to release chemicals.

These cause all the features of asthma, including swelling and narrowing of the bronchi and secretion of thick mucus which make it difficult for patients to breathe.

Dr Djukanovic says they believe the vaccine stimulates a subset of immune
cells which are able to curb this inappropriate response and restore the balance of the immune system.

Allergies to pollen, furry or feathery animals or house-dust mite, can be triggers for asthma, because they irritate the airways.

Previous research has shown children who attend nurseries or those exposed to germs brought home by older siblings had some protection against developing allergies.

Other studies have suggested hay fever was less common among children living on farms.

'Too clean'

Dr Djukanovic added: "This vaccine is based on the idea that we live in an environment that is too clean.

"We have changed the balance of the environment and our bodies have become over-protected through the use of antibiotics, vaccination programmes and cleanliness.

"All this has a knock-on effect, since an allergy is an inadequate response to the environment.

"If we protect children too much from the environment, then their immune system does not learn to respond in a balanced manner."

A spokeswoman for the National Asthma Campaign said previous indications showed the bacteria the vaccine is based on could work.

"Evidence of previous exposures to other bugs in that group have been shown in large group studies (for example in Japan) to be associated with a lower prevalence of asthma.

"These previous studies were in those who were naturally exposed to that group of bacteria and so it is logical for such a trial, to use this particular form, which is an innocuous bug about which a lot is known and little risk of side effects."

Anyone interested in taking part in the study should call: 023 8079 4155 or 023 8079 4597.